We all look forward to the advent of Spring with longer days and warmer weather. Unfortunately, so do the worms! It is usually thought that worms begin to thrive on pasture and in our birds once the ambient temperature stays consistently over 10?C.
Increasingly, worms are more of an all year round phenomenon, but the ’Spring rise’ is an added torment. So now is the time to be thinking about your long term worming strategy.
The worm problem!
Worm infections cause damage to the birds gut. This may result in a variety of problems including:
• Loss of shell colour and strength, yolk colour and egg size.
• Poor body weight gain leading to unevenness or sick birds. Affected birds may be dull and show pale combs.
• Poor feed conversion.
• Increased cannibalism through vent pecking due to straining.
• Increased risk of egg peritonitis.
• Death: In very heavy infestations.
There are three main worms that may cause problems in free range birds:
1) Roundworms (Ascaridia galli)
These are the biggest and most common. They are white, up to two inches long and may be visible in droppings in heavy infections.
2) Hairworms (Capillaria)
These are much smaller (hair-like) and are barely visible with the naked eye but can cause significant damage even in only moderate infestations.
3) Caecal worms (Hetarakis gallinarum)
As their name suggests, these worms spend most of their time in the lower end of the gut, the caecae. Frequently they cause no obvious harm in themselves but can carry another parasite (Histomonas) into the bird. Histomonas is the cause of Blackhead and hence control of one parasite can help to control another. With the increasing incidence of histomoniasis for which there is currently no treatment, the role of regular worming is even more important.
Birds become infected by picking up worm eggs from grass, soil or faeces. The worm eggs need warm, moist conditions to develop outside the bird which is why problems are frequently worse in the Spring and Summer, especially following a wet Spring.
If the situation was as clear cut as this preamble suggests, then why does worm control tend to be so hit and miss?
The answer probably lies in the fact that we don’t spend enough time thinking about how the problem affects our specific sites.
Surprisingly, despite the fact that worms are not a new phenomenon in free range poultry, surveys and investigations on the incidence and control of these parasites are few and far between – especially those related to the types of farming and management practices in place today.
A worm survey To obtain better information about the pattern and prevalence of worms in free range flocks, Scottish Agricultural College, Auchincruive, undertook a small survey a couple of years ago. The results give an interesting insight into the problem and yield some useful suggestions for control strategies.
The survey looked in detail at 27 sites around the country and involved taking dropping samples on four separate occasions from 20 weeks of age, accompanied by the detailed history of worming strategies before, during and after sampling.
What did the survey show? Firstly, 20 of the 27 flocks had evidence of a worm burden at some time during the survey confirming what we already knew - worms are common! The 27th flock was interesting. It was a flock of 6,000 birds wormed at housing with flubendazole in the feed (the licenced wormer, Flubenvet from Janssen), housed on deep litter/slats with a droppings pit, with birds having access to rotation paddocks not used by poultry in the preceding two years.
Worming before coming into lay 20 of the 27 flocks were wormed before coming into lay. All 13 flocks that had been wormed with Flubenvet before coming into lay were tested negative for worms at 20 weeks of age. Of the 7 flocks wormed with an unlicenced or unknown worming product, 5 were still positive for worms at 20 weeks.
When were the worm eggs found? As the flocks got older, they were more likely to be carrying worms and the peak number of worms in individual samples occurred at around the time of peak production.
Does worming in lay help? 14 flocks were wormed with Flubenvet in lay after a positive worm egg count was obtained. 9 of these were negative on subsequent testing and a further 3 had their count reduced by over 90% at the next sampling. The remaining 3 flocks saw their worm burden reduced by between 50 and 90%.
So what does all this tell us?
1) Worms are common and almost inevitable in laying flocks unless birds are effectively wormed before move to laying accommodation and have the luxury of moving to ’virgin’ pasture.
2) Worming prior to the onset of lay with the only licenced wormer means that you ought to at least start production with a clean slate.
3) Worms can build up quickly on the laying site and can peak at a time when birds are trying to reach peak egg production.
4) Worming in lay can remove the offending worm burden.
5) Worming only once during lay may not prevent worms from the pasture re-infecting birds and building up to significant levels, suggesting repeated worming may be necessary.
So how does this affect me on my farm? If you have to ask the question, then the answer is that you need to start looking.
Undoubtedly, some producers have been in business for many years and have never identified a problem. This may be due to a combination of the fact that your pullet rearer has delivered you a clean flock and either by your good management, pasture rotation, soil type and drainage or good old fashioned luck, your birds have not met a challenge during lay. Secondly, your birds may have met a moderate burden which has not had a significant effect on performance – or you just haven’t noticed!
So where do I go from here? Firstly, as we frequently say in these columns, it is important to know your enemy before you can work out what you need to do about it. Worm burdens can be most easily identified by examination of droppings for the presence of visible roundworms although this won’t be any good for looking for hairworms which can frequently be more severe in their damage to bird performance but are too small to see. Therefore, sending dropping samples to your veterinary surgeon gives a more informative answer – twenty fresh dollops taken off the slats is a good sample.
The most accurate strategy is to submit ailing, thin or other culled birds to your vet for a routine post mortem and health screening, where visible and microscopic tests on the gut can be done, often picking up a burden before it becomes ’patent’ ie when birds are pushing out large numbers of eggs that could be detected on a droppings sample.
When do I test? It is a good idea to test your birds via their droppings soon after arrival on site to check they are free before they start to lay. After that, it is worth establishing a programme with your vet. Clearly if you experience a drop in production, loss of egg size or shell colour, it is worth following this up with a dropping sample and ailing or recently dead birds.
If no specific problems are experienced, the survey discussed earlier suggested that peak worm egg output tends to coincide with peak egg production. So a sample taken then, proving negative, gives you a good comfort factor that nothing is really going wrong. A sample late in the life of the flock again gives you a benchmark for your worm control strategy and also lets you know the likely status of that paddock for the next flock in.
Armed with this information, you are either comforted that all is well or you may be less fortunate and uncover a lurking menace. At least in the latter case you know what you are dealing with and could do something about it. So what actions can you take?
• Regular worming, on the basis of previous experience and discussion with your veterinary surgeon.
• Effective paddock rotation, to reduce worm build<
